Green Thoughts: Tales from the undergrowth

Over eons, tropical plants have learnt how to cope with a range of conditions. It is worth noting these strategies. Wherever possible, I like to try and replicate the ways and wherefores of Mother Nature. For example in tropical rainforests, and there were hectares of pristine jungle in Phuket once upon a time, there are distinct micro-climates: all the way up from the understorey level where ground-hugging, moisture-loving and sun-deprived plants clamber amid the organic detritus of leaves and humus, to the canopy where the loftiest trees are bathed in ultra-violet light and the direct caress of rain. There are natural layers in between these domains, but tropical fauna, like tropical flora, find them less important: most creatures are adapted to inhabit either the canopy (monkeys, birds) or the forest floor (deer, shrews, snakes).

Most ground-covering plants are therefore happy to stay that way as they have sophisticated mechanisms for utilizing and photo-synthesizing the limited light (as little as 5%) that reaches the forest floor, and in any case, usually start into growth earlier than tall trees in order to make use of gaps before they are closed by new arboreal growth. Moreover, ground-huggers enjoy the greater humidity and more stable temperatures provided by shaded terrain.

Hence the proliferation of plants explicitly adapted to these conditions – ferns, mosses, ground ivy, and the whole panoply of shade-accepting plants we grow in our living rooms or in areas of our gardens where the sun does not dominate. I am thinking of course of broad-leaved herbaceous plants such as dieffenbachia (dumb cane), aglaonema, massive colocasias (elephant ears), hostas, fatsias, hydrangeas, most bromeliads, coleus, caladium and spathiphyllum lilies. And where will you find them in nurseries? Normally under netting in the shade. Put them in direct tropical sun and they will react badly – either by folding their leaves like a half-closed umbrella or by showing signs of their distress in the form of scorched or yellowed foliage.

Of course there are plants that buck the trend, that try to escape the sepulchral conditions they are born into. Most vines begin life at the dank base of lofty rainforest trees, but then climb unerringly towards the light. Nothing will stop them, their long stems usually armed with tendrils or suckers which grasp the nearest support (passiflora or passion flower, clitoria ternatea or butterfly pea), or which themselves grow in a helix, twining round the host in a bine (ipomoea, honeysuckle, bindweed). Onwards and upwards they go, at an advantage over other plants which need to expend most of their energy in the production of rigid supportive tissue. A climber can root in humus rich soil on the ground-floor, but have most of its leaves 40 feet up in the sunny, exposed elevations, thus getting the best of both worlds.

If you do elect to cultivate ornamental vines in your garden – and they are great at covering unsightly walls or climbing obstacles, ensure two things. One; that their root system is grounded in cool, even moist conditions and two; that you understand the mechanism of attachment. I say this because some vines have little or no way of hanging on. If they do reach the heights, it may be more luck than judgment – unless of course you have taken the trouble to attach them to supports. Some of the best of all so-called climbers come into this category: Allamanda cathartica, the chalice vine, Rangoon creeper and bougainvillea – though the bougainvillea does make use of long and vicious spines to help it hang on to its surroundings.

Which brings me to the initial impetus for this article. Consider this: the ultimate micro-climate for a plant is a pot, where you can vary the soil, the amount of water and fertiliser. And you can experiment with locations; a pot in one situation may enjoy a quite different environment from another sited elsewhere. Let me offer some examples.

I have about 50 plants in large pots around my pool. Incidentally, all of them have plastic saucers which are not only waterproof but make moving containers a whole lot easier. I try to position these potted plants according to their cultural requirements: full sun lovers (bougainvillea, Euphorbia milii, portulaca), dappled shade merchants, and understorey denizens (aglaonema, dieffenbachia, hydrangea and so on).

Pretty straightforward. But why not extend the principle and use the idea of different plants and different conditions in the same container. For instance, try putting tall, leggy, single stemmed plants such as red cordylines or crotons in a pot and cover up the bare stem with bushy or understorey plants such as flowering portulacas, coleus, ruellias, busy lizzies or dwarf ixora which consequently derive some protection from the sun. If you possess a spreading, leafy shrub in a container, you might consider putting a smaller, shade-loving plant beneath. Two for the price of one. A lesson from the rainforest. And the aesthetic benefits as well as the natural ones can make such an experiment worthwhile. Try it! It even makes aesthetic sense.

Patrick has been writing for 10 years about gardening in Phuket and allied topics. If you have horticultural or environmental concerns, please contact him at drpaccampbelll@gmail.com. Many of his earlier creative and academic publications can be found at Wordpress: Green Galoshes.

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